1. Field of the Invention
The present invention relates to a method for producing a semiconductor optical device.
2. Description of the Related Art
An integrated semiconductor optical device containing two optical devices which are optically coupled to each other is known. In general, these two optical devices have waveguide structures. In the integrated semiconductor optical device, the waveguide structures of the two optical devices may have different optical confinement structures from each other. For example, Japanese Unexamined Patent Application Publication No. 7-142699 discloses a method for producing a semiconductor optical device in which a ridge-type optical waveguide and a buried-type optical waveguide are connected to each other. In the method for producing a semiconductor optical device, a SiO2 mask is formed on semiconductor layers grown on a semiconductor substrate. The SiO2 mask is used to form the ridge-type optical waveguide and the buried-type optical waveguide by patterning. A region where the ridge-type optical waveguide will be formed is protected by covering the region with a SiNx mask. A region where the buried-type optical waveguide will be formed is processed with the SiO2 mask into a mesa structure. A buried semiconductor layer is grown on side surfaces of the mesa. The SiNx mask that covers the region where the ridge-type optical waveguide will be formed is selectively removed. The region where the buried-type optical waveguide is formed is covered with a photoresist pattern. The region where the ridge-type optical waveguide will be formed is processed with the SiO2 mask as an etching mask into a ridge structure.